Prior art testers for single-board microprocessor-based controllers having on-board dynamic RAM has required two separate testers, a static tester for the logic and a dynamic tester for the RAM, and has required all RAM data, address and control lines to be brought out to tab pins of the card.
Logic and dynamic RAM has been packaged on a single card. It usually has been a design constraint of being able to electrically isolate the RAM from the logic, and to make all RAM control, address, and data lines available at card I/O's. This has been necessary to accommodate unit testing. Prior art tests have required the use of a static logic tester for the logic and a separate specialized memory tester for the RAM. Two different testers resulted in lost motion thereby increasing unit costs and decreasing manufacturing throughput. Product suffered in that, among other reasons, separate testers were required, and static and functional speed testing did not occur simultaneously. Also, the prior art devices did not provide a self test program with any type of diagnostic capability which isolated to a failing component for AC faults.
The present invention overcomes the disadvantages of the prior art by making a dynamic RAM appear like a static device to an external static tester.